Modified linkbelt molding and throughdrying fabrics

ABSTRACT

Throughdried tissue sheets can be made using a linkbelt throughdrying fabric and/or transfer fabric. In particular, linkbelts can be modified with topically-applied materials, such as extruded or printed silicone materials, in a pattern that provides an overall background texture and/or a decorative design that is imparted to the resulting tissue.

BACKGROUND OF THE INVENTION

In the manufacture of tissue products, it is often desirable to not onlyprovide a product that exhibits good functional properties, but alsoaesthetic properties as well. For example, commonly-assigned WO 01/48310A1 to Burazin et al. published Jul. 5, 2001, entitled “Decorative WetMolding Fabric For Tissue Making” discloses decorative wet moldingfabrics for tissue making in which a textured woven throughdrying fabricis provided with decorative designs using extruded polymeric strands orstitches, for example. While this has been effective, there areinstances where the textured background of the throughdrying fabricmakes it difficult to clearly see the decorative design. To address thissituation, US-2006-0137840-A1 entitled “Textured Tissue Sheets HavingHighlighted Design Elements” and US-2006-0157210-A1 entitled “Method ofMaking Tissue Sheets With Textured Nonwoven Fabrics Having HighlightedDesign Elements” disclose the use of highlight areas surrounding thedesign elements in order to make the design elements more visible. Whileeffective, this approach requires further modification of thethroughdrying fabric, which in some instances may be undesirable becauseof the potential reduction in air permeability of the fabric and hencereduced drying efficiency.

Therefore there is a need for a throughdrying fabric having high airpermeability and which imparts decorative designs to the tissue sheet.

SUMMARY OF THE INVENTION

It has now been discovered that linkbelts, which have been used forpapermaking in other ways, can be especially useful as a molding and/orthroughdrying fabric for making tissues and towels. More specifically,not only can linkbelts be used as a molding/throughdrying fabric, theycan be modified with an unlimited number of surface appearances bytopically applying decorative design elements and/or background textureelements to the surface of the linkbelt to produce a “modified linkbelt”(hereinafter defined). Since linkbelts inherently have a relativelysmooth surface texture, decorative design elements are readily visiblein the resulting sheet without the need for creating surroundinghighlight areas. Enhanced visibility may also be accomplished byprinting a decorative design element within an unprinted surroundinghighlight area, which in turn is surrounded by a patterned backgroundtexture. The relatively smooth surface of the unprinted linkbeltprovides sufficient contrast between the printed decorative designelement, unprinted highlight area, and printed background textureelements. In addition, since linkbelts can be made with very high airpermeability properties, overall background texture elements can also beapplied to the surface of the linkbelt in order to impart athree-dimensional background texture to the resulting sheet while stillretaining good drying efficiency.

Furthermore, linkbelts and modified linkbelts can also be used as atransfer fabric, which is a wet web carrier fabric positioned betweenthe forming fabric(s) and the throughdrying fabric(s) on a tissuemachine, which enables the use of various fabric combinations whenmaking tissues or towels. These combinations include: (a) a linkbelttransfer fabric and a linkbelt throughdrying fabric; (b) a linkbelttransfer fabric and a modified linkbelt throughdrying fabric; (c) alinkbelt transfer fabric and a conventional woven throughdrying fabric;(d) a modified linkbelt transfer fabric and a modified linkbeltthroughdrying fabric; (e) a modified linkbelt transfer fabric and alinkbelt throughdrying fabric; (f) a modified linkbelt transfer fabricand a conventional woven throughdrying fabric; (g) a conventional woventransfer fabric and a modified linkbelt throughdrying fabric; and (h) aconventional woven transfer fabric and a linkbelt throughdrying fabric.In all cases, the wet web can be rush transferred to the linkbelt ormodified linkbelt to impart machine direction stretch to the resultingtissue sheet. When rush transfer is used, the linkbelt or modifiedlinkbelt to which the web is being transferred can be traveling at aspeed of from about 10 to about 80 percent slower than the fabric fromwhich the wet web is being transferred.

Hence, in one aspect the invention resides in a modified linkbelt.

In another aspect, the invention resides in a method of making a tissuesheet comprising depositing an aqueous suspension of papermaking fibersonto a forming fabric to form a wet web having a consistency of fromabout 20 to about 40 percent or greater, more specifically from about 20to about 30 percent, transferring the wet web to a linkbelt andthroughdrying the web to produce a tissue sheet. In this aspect, thelinkbelt can be a transfer fabric and/or a throughdrying fabric.Particularly when the linkbelt is used as a throughdrying fabric, thewet web is conformed to the surface of the linkbelt to impart a mirrorimage of the surface texture of the linkbelt to the dried tissue sheet.

In another aspect, the invention resides in a method of making a tissuesheet comprising depositing an aqueous suspension of papermaking fibersonto a forming fabric to form a wet web having a consistency of fromabout 20 to about 40 percent or greater, more specifically from about 20to about 30 percent, transferring the wet web to a modified linkbelt andthroughdrying the web to produce a tissue sheet. In this aspect, themodified linkbelt can be a transfer fabric and/or a throughdryingfabric. Particularly when the modified linkbelt is used as athroughdrying fabric, the wet web is conformed to the surface of themodified linkbelt to impart a mirror image of the surface texture of themodified linkbelt to the dried tissue sheet. As a result, the tissuesheet exhibits the background texture and/or the decorative design ofthe modified linkbelt.

As used herein, the term “tissue sheet” means a low density paper sheet,such as sheets used for facial tissue, bath tissue, paper towels, tablenapkins and the like. The basis weight can be from about 10 to about 120grams per square meter (gsm), more specifically from about 10 to about45 gsm, more specifically from about 10 to about 35 gsm, morespecifically from about 20 to about 35 gsm, more specifically from about20 to about 30 gsm and still more specifically from about 30 to about 35gsm. Such sheets can also be characterized by a bulk of about 4 cubiccentimeters or greater per gram as measured under a load of about 90grams per square inch (6.45 square centimeters) by conventional methods.For purposes herein, tissue sheets can be made by any throughdryingprocess known in the art which includes the steps of forming, dewateringand throughdrying. The tissue sheets can be creped or uncreped.

As used herein, a “linkbelt” is a papermaking fabric made of a pluralityof spiral coils positioned side-by-side in an overlapping manner tocreate channels and assembled together with a plurality of rods insertedthrough the channels. Such fabrics are disclosed and described in U.S.Pat. No. 4,567,077 issued Jan. 28, 1986 to Gauthier and U.S. PatentApplication No. 2006/0124268 A1 to Billings published Jun. 15, 2006,both of which are herein incorporated by reference. Linkbelts arecommercially available from Albany International under the name“Aerolink” or from Voith Fabrics under the name “Finelink”.

As used herein, a “decorative design” is a decorative figure, icon orshape such as a flower, heart, puppy, logo, trademark, word(s) and thelike. The decorative design can be formed by raised areas (elements)which give the decorative design a topography that distinguishes it fromthe surrounding linkbelt surface. These elements can suitably be one ormore lines, segments, dots or other shapes.

As used herein, the term “textured background surface” means an overallbackground surface having a three-dimensional topography withz-directional elevation differences of about 0.2 millimeter or greater.The topography can be regular or irregular. The background surface isthe overall predominant surface of the fabric, excluding any portions ofthe surface occupied by any highlight areas or decorative designelements. Suitable textured background surfaces include surfacesgenerally having alternating ridges and valleys or bumps anddepressions. To distinguish from decorative designs, the frequency ofalternating ridges and valleys in textured background patterns can beabout 20 or greater per 10 centimeters. Similarly, the density of thebumps and depressions for textured background patterns can be about 3 orgreater per square centimeter.

As used herein, the term “highlight area” means a surface area that hassubstantially less texture than the surrounding textured backgroundsurface, or has no texture, so that the decorative design elements areeasily distinguishable by the user of the tissue sheet. The unmodifiedsurface areas of standard linkbelts are particularly suited forproviding highlight areas since such linkbelts have relatively flatsurfaces.

As used herein, “topically-applied” refers to any method of addingmaterial to or incorporating material within the tissue web-contactingsurface of the linkbelt to alter the surface topography of the linkbeltand the resulting tissue sheet. Particularly suitable methods of topicalapplication are printing or extruding polymeric material onto thesurface. Alternative methods include applying cast or cured films,weaving, embroidering or stitching polymeric fibers into the surface tocreate patterns or embossing. Particularly suitable polymeric materialsinclude materials that can be strongly adhered to the linkbelt and areresistant to thermal degradation at typical tissue machine dryeroperating conditions (120° C. to 210° C.) and are reasonably flexible,such as silicones, polyesters, polyurethanes, epoxies,polyphenylsulfides and polyetherketones.

As used herein, a “modified linkbelt” is a linkbelt having atopically-applied material in the form of a decorative design and/or atopically-applied material in the form of a textured background surface.

The dimensions of the elements (lines, dots, and the like) oftopically-applied materials are such that resulting pattern of elementsis detectable in the resulting tissue. By way of example, extruded linesof material used to create the puppy images in FIG. 1 have a height ofabout 0.35 millimeter (mm). The elements of the other patternsillustrated in FIGS. 2, 3 and 4 are of similar dimensions. In general,the height of the topically-applied elements can be from about 0.2 toabout 2 millimeters, more specifically from about 0.3 to about 1.7millimeters and still more specifically from about 0.4 to about 1.4millimeters. The width of the topically-applied elements can be fromabout 0.2 to about 2 millimeters, more specifically from about 0.3 toabout 1.7 millimeters and still more specifically from about 0.4 toabout 1.4 millimeters.

The air permeability of the linkbelt or modified linkbelt throughdryingfabric of this invention can be about 100 cubic meters per minute persquare meter (m³/min/m²) or greater, more specifically from about 100 toabout 340 m³/min/m² and still more specifically from about 150 to about340 m³/min/m². The air permeability can be adjusted by the design of thelinkbelt, including the diameter of the spiral coils, the geometry ofthe coils, the presence of filler strands within the linkbelt, thetopically-applied textured background pattern, the topically-applieddecorative design elements, etc. Air permeability can be measured by theFrasier air permeability test, Paper Machine Clothing, Sabit Adanur,Technomic Publishing Company (1997) page 89.

The percentage of the surface area of the linkbelt or modified linkbeltoccupied by the topically-applied strands or other elements of thedecorative design patterns or background surface texture patterns can befrom 0 to about 80 percent, more specifically from about 1 to about 80percent and still more specifically from about 5 to about 50 percent.While the air permeability of the modified linkbelt will generallydecrease as the area covered by the topically-applied elementsincreases, the linkbelt design inherently provides for such high levelsof air permeability that in many cases the decrease in air permeabilitywill not be a controlling factor for commercial production.

The fabric support index of the linkbelt or modified linkbelt needs tobe sufficiently high to support the topically-applied material and thefibers in the wet web. In particular, the fabric support index can beabout 20 or greater, more specifically about 25 or greater. The fabricsupport index can be determined by calculation in accordance with PaperMachine Clothing, Sabit Adanur, Technomic Publishing Company (1997),page 90.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a plan view photograph of a modified linkbelt in accordancewith this invention having decorative design elements, namely puppiesand butterflies. The base linkbelt is a Voith Fabrics Finelink BC.

FIG. 2 is a plan view photograph of a modified linkbelt in accordancewith this invention having a decorative design formed by geometricdesign elements comprising intersecting circles (wedding ring pattern).The base linkbelt is a Voith Fabrics Finelink BC.

FIG. 3 is a plan view photograph of a modified linkbelt in accordancewith this invention having a textured background surface formed by aseries of wavy ripples. The base linkbelt is a Voith Fabrics FinelinkBC.

FIG. 4 is a plan view photograph of a modified linkbelt in accordancewith this invention having both decorative design elements and texturedbackground surface elements, namely a printed “Scott” logo decorativedesign element surrounded by a relatively flat unprinted highlight areawithin a printed textured background surface comprising a series ofclosely-spaced four-dot elements. The base linkbelt is a Voith FabricsFinelink BC.

FIG. 5 is plan view photograph of a tissue sheet made using the modifiedlinkbelt of FIG. 2.

FIG. 6 is a plan view photograph of a tissue sheet made using themodified linkbelt of FIG. 3.

FIG. 7 is a plan view photograph of a tissue sheet made using themodified linkbelt of FIG. 4.

EXAMPLES Example 1

In order to further illustrate this invention, a three-layered tissuesheet suitable for single-ply bath tissue was made in which the twoouter layers comprised a debonded mixture of Aracruz eucalyptus fibersand broke fibers and the center layer comprised refined northernsoftwood kraft (NSWK) fibers. Broke fibers comprised 16.5 percent of thesheet on a dry fiber basis. Prior to formation, the outer layer fiberswere pulped for 15 minutes at 10 percent consistency and diluted toabout 2.5 percent consistency after pulping. A debonder (ProSoft TQ1003)was added to the outer layer pulp in the amount of 1 kilogram ofdebonder per tonne of outer layer dry fiber. The NSWK fibers were pulpedfor 30 minutes at 4 percent consistency and diluted to about 2.7 percentconsistency after pulping. The overall layered sheet weight was split 34percent to the center layer on a dry fiber basis and 33 percent to eachof the outer layers. The center layer was refined to levels required toachieve target strength values, while the outer layers provided surfacesoftness and bulk. Parez 631NC was added to the center layer at 1.5kilograms per tonne of center layer dry fiber.

A three-layer headbox was used to form the wet web with the refined NSWKstock in the center layer of the headbox. Turbulence-generating insertsrecessed about 3.5 inches (89 millimeters) from the slice and layerdividers extending about 1 inch (25 millimeters) beyond the slice wereemployed. The net slice opening was about 0.9 inch (23 millimeters). Thewater flows in the headbox layers were split 28.5 percent to each of theouter layers and 43 percent to the center layer. The consistency of thestock fed to the headbox was about 0.1 weight percent.

The resulting three-layered web was formed on a twin-wire, suction formroll former, with the outer forming fabric being an Asten 867A, and theinner forming fabric being a Voith Fabrics 2164-33B. The speed of theforming fabrics was 2000 feet per minute (10.16 meters per second). Thenewly-formed web was then dewatered to a consistency of about 27-29percent using vacuum suction from below the forming fabric before beingtransferred to a transfer fabric, which was traveling at 1600 feet perminute (8.13 meters per second) (25 percent rush transfer). The transferfabric was a Voith Fabrics t1207-6. A vacuum shoe pulling about 10inches (254 mm) of mercury rush transfer vacuum was used to transfer theweb to the transfer fabric.

The web was then transferred to a Voith Fabrics Finelink BC linkbeltthroughdrying fabric modified with a printed pattern as shown in FIG. 3.The air permeability of the modified linkbelt was about 150 m³/min/m².

A vacuum transfer roll was used to wet mold the sheet into thethroughdrying fabric at about 8 inches (203 mm) of mercury wet moldingvacuum. The throughdrying fabric was traveling at a speed of about 8.13meters per second. The web was carried over a pair of Honeycombthroughdryers operating at a supply temperature of about 390° F. (199°C.) and dried to final dryness of about 99 percent consistency.

The resulting tissue is shown in FIG. 6. It had a basis weight of 31.0gsm, a geometric mean tensile strength of 704 grams per 7.62 centimetersof width, a ratio of the machine direction tensile strength to thecross-machine direction tensile strength of 1.72, and a caliper of 840microns.

Example 2

Tissue sheets were made as described in Example 1, except that the speedof the forming fabrics was 2048 feet per minute (10.40 meters persecond, 28% rush transfer) and the throughdrying fabric was a VoithFabrics Finelink BC linkbelt modified with a printed pattern as shown inFIG. 4. The air permeability of the modified linkbelt was about 160m³/min/m².

The resulting tissue is shown in FIG. 7. It had a basis weight of 31.2gsm, a geometric mean tensile strength of 936 grams per 7.62 centimetersof width, a ratio of the machine direction tensile strength to thecross-machine direction tensile strength of 1.83 and a caliper of 853microns.

Example 3

Tissue sheets were made as described in Example 2, except that thethroughdrying fabric was a Voith Fabrics Finelink BC linkbelt modifiedwith a printed pattern as shown in FIG. 2. The air permeability of themodified linkbelt was about 220 m³/min/m².

The resulting tissue is shown in FIG. 5. It had a basis weight of 31.1gsm, a geometric mean tensile strength of 830 grams per 7.62 centimetersof width, a ratio of the machine direction tensile strength to thecross-machine direction tensile strength of 1.75, and a caliper of 644microns.

It will be appreciated that the foregoing examples, given for purposesof illustration, are not to be construed as limiting the scope of thisinvention, which is defined by the following claims and all equivalentsthereto.

1. A method of making a tissue sheet comprising depositing an aqueoussuspension of papermaking fibers onto a forming fabric to form a wet webhaving a consistency of from about 20 to about 40 percent, transferringthe wet web from the forming fabric to a modified linkbelt transferfabric and throughdrying the web to produce a tissue sheet.
 2. Themethod of claim 1 wherein the wet web is transferred from the modifiedlinkbelt transfer fabric to a linkbelt throughdrying fabric.
 3. Themethod of claim 1 wherein the wet web is transferred from the modifiedlinkbelt transfer fabric to a modified linkbelt throughdrying fabric. 4.The method of claim 1 wherein the wet web is transferred from themodified linkbelt transfer fabric to a conventional woven throughdryingfabric.
 5. The method of claim 1 wherein the consistency of the wet webis from about 20 to about 30 percent.
 6. The method of claim 1 whereinthe throughdried web is creped.
 7. The method of claim 1 wherein thethroughdried web is uncreped.
 8. The method of claim 2, 3 or 4 whereinthe speed of the throughdrying fabric is from about 10 to about 80percent slower than the speed of the forming fabric.
 9. The method ofclaim 1, 2, 3 or 4 wherein the speed of the transfer fabric is fromabout 10 to about 80 percent slower than the speed of the formingfabric.